Elevated blood pressure is associated with increased risk for coronary heart disease and stroke. It is clear that diet plays an important role in modulating blood pressure with excess intake of alcohol, sodium and calories leading to elevated blood pressure. However, the role of other dietary constituents in modulating blood pressure requires further study. Employing a multi-center approach in which each center follows a common protocol, the proposed study addresses key issues regarding the relationship between diet and blood pressure. We hypothesize that selectively modifying the overall macronutrient or the specific micronutrient composition of the diet will have a beneficial effect on blood pressure, and that a combination of the modifications will have an even greater beneficial impact on blood pressure. To test this hypothesis, we propose a randomized, double blind, parallel- arm design, to examine the effect on blood pressure of a favorable macronutrient dietary pattern and a favorable micronutrient dietary pattern in a 2 x 2 factorial design consisting of four diets: 1. The Usual American Diet (modified to reflect African American eating patterns). 2. The Usual American Diet modified to reduce total fat and increase protein and dietary fiber. 3. The Usual American Diet modified to increase calcium, magnesium and potassium with foods rather than supplements. 4. The Usual American Diet modified to reduce total fat and increase protein and fiber and modified to increase calcium, magnesium and potassium. We propose to study the effect of these dietary patterns in a population of approximately 512 (128 at each Field Center) predominantly African American adult men and women with borderline or mild hypertension. The proposed study will examine these subjects in four cohorts over a two year period; each cohort will be studied for a 16 week period consisting of a 4 week "run-in" period, followed by 12 weeks of dietary study. In addition to comprehensively monitoring blood pressure, we also propose to study mechanisms which may underlie the diet-induced changes in blood pressure. These include studies of insulin sensitivity, physical fitness and body composition. To conduct the proposed study, the Pennington Biomedical Research Center has assembled a team of investigators with experience in the areas of hypertension, clinical studies, human nutrition feeding trials, multicenter studies, dietary nutrient analysis, dietetics, biostatistics, metabolism, behavioral psychology and minority recruitment. This interdisciplinary approach should ensure the successful execution of the proposed studies.